This invention relates to the art of shift registers and more particularly, to magnetoresistance circuits and processes for sensing magnetic field patterns on thin magnetic film memories.
Prior art thin magnetic film memory devices rely upon detection of the modulation of a high frequency electromagnetic wave by ferromagnetic resonance absorption, e.g., U.S. Pat. No. 3,629,520, or detection of domain wall creep in response to application of a local magnetic field, e.g. U.S. Pat. No. 3,868,660. The bit density and the suitability for multi-unit fabrication of thin magnetic film strip memories available through the teachings of recent disclosures in the thin-film memory art and such novel features as the stable domain wall core disclosed in copending U.S. Patent application Ser. No. 877,632, Serriform Strip Crosstie Memory, L. J. Schwee, H. R. Irons, and W. E. Anderson, Navy Case No. 62,713, are incompatible to multilayered detection devices dependent upon ferromagnetic resonance phenomena.
A recent issue, U.S. Pat. No. 4,100,609, discloses a single layer magnetoresistance circuit for detecting the presence or absence of Bloch line-crosstie pairs at selected locations along a crosstie memory strip. The device taught there depends upon an electrical current flowing diagonally across the thin film layer through a central electrode spaced between a pair of electrodes adjoining one or both of the margins. That structure inherently confines the detector to the area between the pair of electrodes.